Electrophoretic display media, generally characterized by the movement of particles through an applied electric field, are highly reflective, can be made bistable, can be scaled to a large area, and consume very little power. Encapsulated electrophoretic displays also enable the display to be printed. These properties allow encapsulated electrophoretic display media to be used in many applications for which traditional electronic displays are not suitable, such as flexible displays.
One particular application for displaying screens are input devices, such as touch screens or keypads, or writing tablets. In many cases, it is desirable to sense the state of the display in order to digitize the input. For example, measuring and analyzing certain properties of the display may enable detection of the location of the input. A responsive event or action may then be generated.
Also, the electrical properties of encapsulated electrophoretic display media may vary in response to environmental factors, such as temperature and humidity. In some circumstances, in order to achieve a repeatable optical state in the display, it may be desirable to compensate the drive waveform in response to changes in electrical properties of the polymeric materials that comprise encapsulated electrophoretic display media. Thus, it is desirable to measure the display parameters that affect waveform compensation scheme. Use of external display sensors, however, may increase cost of the display and complicate the manufacturing process. In addition, external sensors may not accurately measure the parameters inside the display.